Assessing the carbon footprint of converting confinement dairy production to seasonal grazing in a dairy herd: a scenario study

Calf diarrhea, one of the most common stresses causing by heifer rearing, affects most Chinese dairy herds, yet its long-term consequences on lactation performance remain poorly quantified. This study explored whether calf diarrhea has a long-term effect on the lactation performance and Dairy Herd Improvement (DHI)-related indices of dairy cows and its influence during different lactation periods. This retrospective study included a total of 1,907 Holstein dairy cows from a large-scale farm in northern China (700 in the diarrhea group and 1,207 in the healthy group). A mixed effects model and mediation analysis were used to evaluate the effects of calf diarrhea on growth performance, milk yield, milk composition and other lactation parameters at different parities and lactation periods. The results revealed that the negative effect of calf diarrhea on lactation performance was persistent and varied by parity. The 305-d milk yield and peak milk yield of cows at each parity in the diarrhea group were significantly lower than those in the healthy group (P < 0.05). Growth performance, such as withers height (median: 134.00 vs. 135.00 cm), was more significantly affected in the first parity (P < 0.001). With increasing parity, the difference in body condition scores narrowed, but the loss of milk production continued to accumulate. For the second and third parities, cows with calf diarrhea presented significant reductions in 305-day milk yield, with decreases of 287.36 kg and 1,086.76 kg in the median comparison, respectively (P < 0.05). The corrected milk yield and milk fat percentage during the early postpartum and early lactation periods decreased more significantly in multiparous cows, and the daily milk production in the middle and late lactation periods remained consistently lower than that in the healthy group (P < 0.05). Mediation analysis confirmed that milk production played a key mediating role in the pathway by which diarrhea affected the milk fat percentage. Our research revealed that calf diarrhea is a critical early-life health challenge, with consequences extending beyond the calf period to significantly affect lactation potential. Our findings underscore the need for early-life interventions to mitigate lactation losses in high-parity herds.

Bovine paratuberculosis (PTB), caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic infection that undermines cattle productivity and farm profitability. In Bangladesh, no previous studies have estimated PTB prevalence or identified associated risk factors. This cross-sectional study (January 2023 to December 2024) was conducted across 14 districts and 138 dairy farms to estimate true MAP antibody prevalence and identify factors associated antibody detection. Bulk milk samples from all herds (n = 138) and 880 individual milk samples from ELISA-positive herds were tested using a commercial indirect ELISA. True herd- and cow-level antibody prevalence was estimated using Bayesian latent class models. Risk factors were identified using multivariable logistic regression (herd-level) and mixed-effects logistic regression (cow-level). The apparent antibody prevalence was 7.2% at the herd-level and 12.2% at the cow-level, with herd-level prevalence ranging from 0.9% to 37%. After adjusting for test sensitivity and specificity, true antibody prevalence estimates decreased to 4.9% (herd level) and 9.4% (cow level). Herds with more than two retained placenta cases had significantly higher odds of MAP antibody detection (odds ratio [OR] = 9.42) than herds with two or fewer such events. At the cow level, older age (>7.9 years) was associated with higher odds of antibody positivity compared with cows ≤4 years. Cows with anestrus (OR = 3.89) or repeat breeding (OR = 2.63) had significantly higher odds of MAP antibody detection compared with cows without these disorders. Milk antibody levels showed a negative association with milk yield, with each unit increase in the sample-to-positive ratio corresponding to a 0.018 L/day reduction. These findings indicate that apparent antibody prevalence substantially overestimates PTB exposure in the study areas. The associations with retained placenta, anestrus, and repeat breeding suggest potential reproductive impacts that warrant further investigation. Given the purposive sampling strategy and reliance on milk ELISA, the results should be interpreted within the context of the study population. Enhancing diagnostic capacity and integrating PTB considerations into reproductive herd management may help reduce productivity losses, while larger, probability-based studies are needed to assess the national burden.

Clinical data on antimicrobial profiles are useful for dairy udder health treatment programmes and represents a component of antimicrobial stewardship. The study aimed to determine the bacterial aetiology of clinical mastitis in dairy herds in Western Australia and to evaluate their antibiotic resistance profiles. This retrospective study utilised clinical antimicrobial profile data from two referral diagnostic centres within the region of Western Australia. A total of 545 mastitic samples were submitted for antimicrobial culture and testing over a period of 10 years (2008–2018). Of these, 406 showed bacterial growth and 139 no bacterial growth was observed. The most common isolates were Streptococcus uberis (25.3%), Staphylococcus aureus (17.2%), and Escherichia coli (9.4%). No growth was identified in 25.5% of the mastitis milk samples. The antimicrobial profiles revealed high susceptibilities towards cefuroxime (95.7%), clavulox (89.4%), and oxytetracycline (89%), whilst showing high resistance towards novobiovin (70%). From this study, it is concluded that there was a decline in the resistance trends towards the isolates of both S. uberis and S. aureus over the 10-year period and contagious mastitis had a higher occurrence. There is a need to consider surveillance programmes that determine the patterns of on-farm antimicrobial usage and further characterise the pathogens based on the presence of resistance antimicrobial genes. Data on antimicrobial surveillance represent an important component of antimicrobial stewardship.

Milk production and quality are increasingly affected worldwide by rising ambient temperatures associated with climate change, with heat stress (HS) representing one of the major environmental challenges for dairy cattle. HS alters physiological and metabolic processes, leading to significant changes in milk composition, particularly in regions exposed to prolonged summer heat. The Temperature–Humidity Index (THI) is widely used to assess the degree of thermal discomfort and its impact on dairy performance. This study investigated the effects of heat stress on milk quality parameters in a dairy herd managed under identical conditions, comprising Romanian Black Spotted (RBS, Holstein strain) and Romanian Spotted (RS, Simmental strain) cows. Descriptive statistics were performed using the SAVC for Windows program, while differences between means were evaluated using the t-test in GraphPad Prism 9. Milk quality traits were significantly affected when THI values exceeded 73, with a consistent decline observed from early summer onwards. In the RBS breed, milk protein content decreased significantly compared with spring values, reaching 3.25% (p &lt; 0.0001) in 2023 and 3.35% (p &lt; 0.01) in 2024. Similar trends were recorded in the RS breed, with minimum protein values of 3.10% (p &lt; 0.0001) and 3.19% (p &lt; 0.0001). Fat content, casein concentration, and milk urea levels also showed highly significant HS-related changes (p &lt; 0.0001). Overall, heat stress negatively affected milk quality, while the RS breed appears less affected under the studied conditions than the RBS breed.

Effective nitrogen management in dairy cow diets is essential for optimising milk production and minimising environmental nitrogen emissions. This study develops a simplified model to estimate nitrogen excretion in dairy farms, distinguishing excretion by animal category (lactating cows, heifers, calves) and organic matrix (faeces, urine), with nitrogen intake as a key input. A comprehensive literature review guided the selection of equations for estimating nitrogen excretion based on dietary nitrogen content, dry matter intake and milk yield. The model was specifically calibrated for Holstein dairy herd in the Po Valley (Italy) context using data collected from ten Lombardy dairy farms over 30 months, focusing on diet composition and nitrogen excretion via faeces, urine, and milk. Validation against established the literature and the Nitrates Directive (91/676/EEC) excretion factors demonstrated the model's alignment in estimating nitrogen excretion. Within this context, the proposed framework may support nitrogen management at farm level by providing a practical, descriptive tool to explore nitrogen flows and to identify potential areas for improving nutrient efficiency and reducing environmental impacts.

Mastitis remains one of the most economically important diseases in dairy farming. The aim of this review was to discuss the main ideas, practical benefits, economic impacts, rules and regulations, and environmental aspects of selective dry cow therapy (SDCT) as a means for managing udder health and antibiotic use. Interest is increasing in antimicrobial resistance, environmental pollution, and stronger regulations on antibiotic use in food production, so SDCT has become even more relevant in modern dairy herd management. This method involves selectively treating only cows or quarters at a high risk of intramammary infections at dry-off, mainly based on somatic cell count, clinical history of mastitis, or bacterial culture results. Evidence shows that when used correctly, SDCT can significantly reduce antibiotic use without compromising udder health, particularly if used with internal teat sealants. Economic analyses have indicated that SDCT can cut antibiotic-related costs by up to 50% while keeping mastitis under control, if protocols are followed properly. Global policies, such as the European Green Deal and One Health initiatives, encourage targeted antibiotic use to improve both animal health and environmental conservation in dairy farming. However, challenges still remain in implementation, including the risk of under-treatment, the need for accurate diagnostic tools, and ensuring farmer compliance with selection protocols. Advanced developments in precision dairy farming, such as automated testing and AI-assisted decision-making, have improved the feasibility and success of SDCT in different herd management systems.

Efforts to improve efficiency and profitability on dairy farms have renewed focus on how culling practices affect herd sustainability and economic outcomes. This study surveyed decision-makers on 60 high-producing, freestall-housed dairy farms in Wisconsin, with a mean (SD) turnover rate of 36.0 (8.0)%. Using a structured questionnaire, we examined herd management, culling criteria, and motivations. Most farms (93%) used on-farm management systems to guide culling, yet only 48% used designated reports, relying instead on individual cow records. Milk production, infertility, and somatic cell count were the top culling criteria, with high milk yield cited as the most difficult factor in removal decisions. While 54% recorded the most obvious reason for culling, only 7% documented multiple causes. Cull cows were typically transported by third parties; 80% farms sent cows directly to slaughter, while 52% sent them to auction. One-third of farms sold cows for continued dairy use. Euthanasia was performed on 93% of farms, mostly by employees, with minimal veterinary input. The study aimed to investigate producer perspectives on the culling decision-making process on commercial dairy farms. The findings highlight opportunities for improved veterinary involvement and the use of structured herd-level reports to support more strategic culling decisions.

In high-producing dairy systems, the average productive lifespan of cows is around 2.5-4years. Persistent productivity and longevity are key determinants of dairy cow production performance and herd profitability. Although gastrointestinal microbiota influences dairy cow productivity, the mechanisms by which host-microbiome interactions support sustained productivity in long-lived dairy cows remain unclear. Therefore, this study integrated the metagenomics and metabolomics of the rumen and rectum, along with serum and milk metabolomics, to elucidate the potential impact of the rumen and rectum microbiota on the productivity of long-lived dairy cows. Serum alanine aminotransferase (ALT), alkaline phosphatase (ALP), total cholesterol (TC), and high-density and low-density lipoprotein cholesterol (HDL-C and LDL-C) levels in long-lived dairy cows were positively correlated with milk yield (MY) and elevated in long-lived high-yielding (LH) dairy cows, whereas insulin (INS) and glucagon (GCG) were negatively correlated with MY and higher in long-lived low-yielding (LL) dairy cows. Rumen propionate level was elevated in LH group and positively correlated with MY. The rumen microbiome, in LH cows upregulated pathways involved in amino acid, cofactor, and vitamin metabolism. LH cows' rumen and rectum microbial networks had cohesion and vulnerability levels similar to those of LL cows and exhibited dependence on key nodes. The rumen and rectum MY-associated purine metabolites, guanosine and D-ribose-1-phosphate, mediated 65.56% and 67.55% of the significant positive effects of Acidaminococcaceae bacterium and Parabacteroides sp. on MY, respectively. Furthermore, the specific lipid metabolism-associated rumen microbiota module enhanced serum eicosapentaenoic acid (EPA) levels by modulating rumen α-linolenic acid metabolism, thereby promoting the synthesis of Pe(20:5/0:0) in milk, which positively contributed to MY. This study revealed the potential contributions of the rumen and rectum microbiota to the productivity of long-lived dairy cows via purine metabolites, as well as the potential role of the rumen microbial network module in influencing productivity through α-linolenic acid metabolism, providing new insights for nutritional management strategies aimed at improving the persistent production capacity of dairy cows. Video Abstract.

Using artificial intelligence to make feeding and management decisions in dairy herds

Mastitis management in automatic milking systems (AMS) is challenging, as detection of clinical signs relies on sensors. Treatment recommendations for clinical mastitis (CM) advise conducting microbiological cultures of the infected quarter whenever possible to guide therapy. The objective of this study was to evaluate the association between the use of a rapid diagnostic mastitis pathogen chromogenic culture test on the CM case duration and the probability of more than one treatment before cure. A total of 106 CM cases from 65 dairy cows housed in a freestall AMS barn were retrospectively analysed: 25 treated according to chromogenic culture results and 81 without pathogen identification. All cases were pre-identified using AMS-derived milk parameters, confirmed through veterinary examination, and followed by weekly veterinary examinations until cure. Generalized mixed linear models were used to assess the association between chromogenic culture use and the outcomes, with confounders included as covariates. The use of a chromogenic culture reduced mastitis case duration by 2.78 ±1.26days compared to treatment without chromogenic culture. There was no effect on the likelihood of affected cows receiving more than one treatment for CM. The use of a chromogenic culture reduced CM time-to-cure in an AMS freestall dairy herd.

Classification of lameness in dairy cows using automatic milking system data and body condition score with machine learning.

Automating classification of veterinary biosecurity recommendations using machine learning.

A cross-sectional study on herd-level risk factors associated with Salmonella Dublin in dairy herds from Québec, Canada.

Differences in reproductive and productive performance and removal from the herd associated with time to clinical cure in dairy cows treated for metritis.

Carbon footprint of milk production systems in El Salvador: differences between specialized dairy and dual-purpose herds and mitigation opportunities

The basis for a cow’s future milk production is laid during the period of active growth and development of replacement heifers. Therefore, many scientists and specialists studying the productivity of current dairy herds worldwide emphasize the need for a meticulous approach to feed selection and rearing techniques for heifers planned for subsequent integration into the main production herd. The purpose of this research was to analyze the effectiveness of using the complex functional additives Rumenfit 100 and Rumenfit 50 in a replacement heifer feeding program and their subsequent impact on the milk production of first-calf heifers. The results of a scientific and economic experiment carried out on animals of Holstein breed from birth to the end of their first lactation at a modern livestock complex have been presented in the article. The active phase of the experiment involved the formation of one control and two experimental groups of 10 animals in each. in each. The housing, microclimate system and care of the experimental animals were identical, the only difference was that in the period from 2 to 6 months of age, the heifers of the 1st experimental group received a complex functional additive Rumenfit 100 as part of the starter compound feed at a rate of 10 g/head day, and the heifers of the 2nd experimental group received a complex functional additive Rumenfit 50 at a rate of 5 g/head/day. At the same time, the growth and development indicators of the heifers were monitored, and the future reproduction indicators were assessed. Finally, the milk productivity of fi rst-calf heifers at the end of lactation was assessed. It was found that first-calf heifers of the control group were inferior in milk yield for 305 days of lactation to their herdmates in the 1st and 2nd experimental groups by 945.5 and 579.5 kg.

Optimal cutoff estimation and evaluation of direct and indirect diagnostic methods for assessing bovine colostrum quality with Bayesian finite mixture models.

Biosecurity in dairy calf production: A scoping review.

Effects of dietary fat supplementation on enteric methane mitigation and farm profitability: A case study of an organic and a conventional dairy herd